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106               PRACTICAL ORGANIC CHEMISTRY     \
a little cold water, and dissolve the sodium salt in hot
water. On cooling, a thick gelatinous mass of sodium
palmitate separates. See Appendix, p. 258.
Glycerol (Glycerin), CHS(OH).CH(OH).CH2(OH)
Scheele, Opusc^ 1779, 2, 175.
Glycerol is obtained by the hydrolysis of fats and oils, and
purified by distillation under reduced pressure with superheated
Properties.A viscid, colourless liquid, with a sweet taste; m.'p.
17, b. p. 290. It boils, under ordinary pressure, with partial
decomposition forming acrolein ; sp. gr. 1*269 at I2 J miscible
with water and alcohol ; insoluble in ether and the hydrocarbons.
Reactions.i. Heat a few drops of glycerol with some powdered
potassium hydrogen sulphate. The irritating smell of acrolein
is at once perceptible.
2. Make a borax bead and dip it into a solution of glycerol
and bring it into the flame. A green colouration due to boric
acid is produced.
Formic Acid, H.CO.OH.
Berthelot, Ann. Chim. P/iys.,ri&$6, (3) 46, 477 ; Lovin, Bull.
Soc. Chim., 1866, (2) 5, 7 ; 1870, (2) 14, 367.
50 gnns. anhydrous glycerol.
200          oxalic acid (in four portions of 50 grams).
The glycerol is dehydrated by heating it gently in a basin on
a sand-bath until a thermometer with the bulb immersed in the
liquid indicates 175. Fifty grams of commercial crystallised
oxalic acid and 50 grams of glycerol are heated in a retort
(250 c.c.) over wire-gauze, with condenser and receiver. A
thermometer is fixed through the tubulus with the bulb in the
liquid. The reaction begins at about 80, and at 90 proceeds
briskly, carbon.dioxide being evolved. The temperature is main-
tained at 105 110 until the evolution of gas has slackened.
Some aqueous formic acid has meanwhile collected in the